Malware (such as viruses, trojans, and other malicious software) has become increasingly difficult to protect against. Various methods have been used to combat malware but more sophisticated malware continues to abound. Malware has been included in often-used types of files, such as word processing, spreadsheet, presentation, and multimedia files. Some malware is difficult to detect using traditional methods because they are embedded in such files. The use of virus signatures to detect malware has been prevalent, but the signatures are very specific and are difficult to maintain in light of obfuscation and other techniques employed by malware authors. This leaves systems vulnerable.